The invention relates to a method of reducing cross talk during signal coupling (hereinafter referred to in shorter convenience as signal coupling) in a connector for the transfer of balanced electrical high frequency signals, said connector comprising contact springs and terminals as well as a plurality of pairs of conductors arranged in an insulation member to connect the contact springs and the terminals, each said pair of conductors being capable of transferring one of the balanced signals.
The invention moreover relates to a connector for the transfer of balanced electrical high frequency signals, said connector comprising contact springs and terminals as well as a plurality of pairs of conductors arranged in an insulation member to connect the contact springs and the terminals, each said pair of conductors being capable of transferring one of the balanced signals.
The invention also relates to a connecting element comprising a plurality of pairs of conductors arranged in an insulation member for the transfer of balanced electrical high frequency signals, each said pair of conductors being capable of transferring one of the balanced signals.
The invention finally relates to a cable which is terminated by a connector at one or both ends.
The transfer of data at very high transmission rates in cables connected by plugs or connectors which may contain many conductors, involves the known problem that so-called crosstalk may occur between the various conductors, which means that signals carried through a conductor will give an unintentional signal contribution through another conductor because of the inevitable capacitance which exists between the conductors. This is aggravated particularly by the circumstance that the distances between the conductors are typically very small so that the size of the capacitances becomes significant.
The patent literature describes many ways of minimizing crosstalk in plugs which are used for high frequency data transfers.
Particularly plugs connecting cables involve a great risk of undesired crosstalk.
A plug for high transmission data usually consists of terminals at one end which are intended to be connected to a cable, a printed circuit board or the like. A connecting element extends from the terminals, consisting of a number of conductors which are arranged in e.g. a dielectric. A plurality of contact springs corresponding to the plurality of conductors is arranged at the other end of the conductors. The contact springs are intended to make contact with another plug. Usually, the contact springs are very closely spaced, which means that the conductors, which are also called connecting conductors below, are very close in the area in which the connection between the contact springs and the connecting conductors is established.
To prevent the previously mentioned crosstalk, the most simple solution is to make the distance between the connecting conductors in the area where the terminals are present, as great as possible. This solution, however, does not compensate the crosstalk, which occurs in the area where the connecting conductors are connected to the contact springs.
Another way of minimizing crosstalk, cf. e.g. U.S. Pat. No. 5,186,647, comprises crossing the pairs of conductors in the area where the contact springs are connected to the connecting conductors. This way of reducing the crosstalk involves a balanced capacitive coupling from each conductor to a conductor of another pair. Signal coupling from the individual conductor will have the same size and polarity to both conductors from another pair, and since only differential signals are of importance, this influence will not be regarded as crosstalk. A possible influence from the pair of conductors to the individual conductor in another air will neutralize itself, since crosstalk contributions from each pole in the pair of conductors gives a capacitive coupling of almost the same size with identical and opposite polarity, which means that the crosstalk contributions will therefore neutralize themselves. The crosstalk occurring between the conductors in the connector is compensated in this manner.
Finally, the art includes a method in which compensation capacitances are added between the connecting conductors which are mounted on e.g. a printed circuit board.
Accordingly, an object of the invention is to provide a method of the type stated in the introductory portion of claim 1 which ensures a minimum of crosstalk in a connector which is used for the transfer of data.
The object of the invention is achieved in that the pairs of conductors in the insulation member are positioned in two mutually spaced layers in such a manner that each of the two conductors belonging to a pair is arranged in a layer of its own, and that said insulation member is made of at least two dielectrics with different permittivity.
Hereby, a possible influence from the individual conductor will be of the same size and have the same polarity for both conductors from another pair, and since only differential signals are of importance, this influence will not be regarded as crosstalk. A possible influence from the pair on the individual conductor will neutralize itself, as crosstalk contributions from each pole give a capacitive coupling of almost the same size with identical and opposite polarities and will therefore neutralize themselves.
Crosstalk occurring in the contact spring part will be compensated by adding an unbalanced capacitive contribution between the conductors of a pair and a conductor or a pole from another pair in the connecting conductors near the contact springs. All things considered, the invention thus provides a method which partly neutralizes the influence from a pole in a pair of conductors on both poles in another pair of conductors, and partly neutralizes a contribution from two poles in a pair to a pole of another pair, as well as compensates crosstalk which occurs in plugs and the contact conductor part.
It is expedient that the one dielectric used is atmospheric air.
The one dielectric is provided as a notch in the insulation member. This may be done relatively simply.
If it is desired to have a connector which must not be made physically weaker, it may be an advantage, that the notch is filled with a dielectric with another permittivity which has a lower value than the notched material.
As mentioned, the invention also relates to a connector. This connector is of the type stated in the introductory portion of claim 5 and is characterized in that the pairs of conductors in the insulation member are placed in two mutually spaced layers in such a manner that each of the two conductors associated with a pair is arranged in a layer of its own, and that said insulation member comprises at least two dielectrics with different permittivity.
This connector, of course, has the advantages which have already been explained in connection with claim 1.
As mentioned, the invention also relates to a connecting element. This connecting element is characterized in that the pairs of conductors in the insulation member are placed in two mutually spaced layers in such a manner that each of the two conductors belonging to a pair is arranged in a layer of its own, and that said insulation member comprises at least two dielectrics with different permittivity.
Finally, as mentioned, the invention relates to a cable, i.e. a cable which is terminated by a connector according to the invention at one or both ends.